At present, pay-per-view cable television systems have two problems. Either they are very complicated, require active circuits, and are therefore expensive to implement or, on the other hand, they are inexpensive to implement but insufficiently secure. The inexpensive, relatively insecure type of system involves the generation of a signal within the video baseband of the program to be denied, insertion of the signal into the transmitted video signal and use of the filter at the subscriber end to remove the unwanted carrier. This system is disclosed in U.S. Pat. No. 4,074,311. A passive filter at the subscriber end allows the unwanted carrier to be removed, thereby causing clear reception of the desired program. This approach is economically attractive, but possession of the filter allows the subscriber to decode all future programs, since all are scrambled in the same way.